Fluorescence refers to the short-duration, spontaneous emission of light of one wavelength upon transition of an excited electron state to a lower-energy state following excitation with light, or electromagnetic radiation in general, of a different wavelength. There are numerous natural and synthetic substances or compounds in which the phenomenon of fluorescence occurs, and which are therefore referred to as fluorophores.
In fluorescence spectroscopy, there is a need for fluorescence standards in order to have reference points for the measurements to be undertaken. Conventional fluorescence standards or fluorescent dyes generally are composed of organic compounds. The basis for these fluorescent dyes is that the molecules of the fluorescent dye emit a portion of the absorbed energy as fluorescent light at a known, different wavelength when they are irradiated with visible or ultraviolet light. These dye molecules are used in a variety of different biological assays, for example, where the fluorescence signals they emit can provide information about the system under study.
However, the prior art fluorescence standards and fluorescent dyes have one or more of the following disadvantages: They are not stable over the applicable time period, fade easily (especially under extended illumination and when illuminated with high intensities), are usable only within a narrow spectral range, are costly, are mechanically, thermally, and chemically unstable, and can age or dry out, which results in a change in the fluorescence intensity.
The object of the present invention is to provide a fluorescence standard that does not suffer the above disadvantages.